30:T69d,initial = { const track = {} const curves = [] const carts = [] for (let y = 0; y < lines.length; y++) { const line = lines[y] for (let x = 0; x < line.length; x++) { const ch = line[x], p = [x,y] const node = { ch, p } switch (ch) { case '>': case '<': case '-': node.ch = '-' node['>'] = [x+1, y] node['<'] = [x-1, y] break case '^': case 'v': case '|': node.ch = '|' node['^'] = [x, y-1] node['v'] = [x, y+1] break case '\\': case '/': curves.push(node) break; case '+': node['^'] = [x, y-1] node['>'] = [x+1, y] node['v'] = [x, y+1] node['<'] = [x-1, y] break; default: } if (ch !== ' ') { track[p] = node if (ch === '>' || ch === '<' || ch === 'v' || ch === '^') carts.push({ p, ch, changes: 0 }) } } } for (const curve of curves) { let n = [curve.p[0], curve.p[1]-1], e = [curve.p[0]+1, curve.p[1]], s = [curve.p[0], curve.p[1]+1], w = [curve.p[0]-1, curve.p[1]] switch (curve.ch) { case '\\': if (track[w]) { // w, s curve['<'] = w curve['v'] = s } else { // e, n curve['^'] = n curve['>'] = e } break case '/': if (track[e]) { // e, s curve['>'] = e curve['v'] = s } else { // n, w curve['^'] = n curve['<'] = w } break } } return { track, carts } }31:[] 2e:{"title":"Day 13","cells":[{"id":0,"value":"md`# Day 13`","pinned":false,"hidden":false,"mode":"ojs"},{"id":352,"value":"trackSVG = {\n const height = width\n const svg = d3.select(DOM.svg(width, height))\n \n const tracks = Object.values(track)\n const max = d3.max(tracks, d => d.p[1])\n \n const zoom = width / (max+1)\n const grid = svg.append('g')\n .attr('transform', `scale(${zoom},${zoom})`)\n \n grid.selectAll('rect')\n \t.data(tracks)\n \t.enter().append('rect')\n .attr('x', d => d.p[0] + .25)\n \t .attr('y', d => d.p[1] + .25)\n .attr('width', .5)\n .attr('height', .5)\n .style('fill', 'lightgray')\n \n return svg.node()\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":274,"value":"{\n const svg = d3.select(trackSVG)\n const grid = svg.select('g')\n \n const circles = grid.selectAll('circle')\n .data(part2.carts)\n \n circles\n .enter().append('circle')\n .attr('r', .5)\n .merge(circles)\n .attr('cx', d => d.p[0] + .5)\n .attr('cy', d => d.p[1] + .5)\n .style('opacity', d => d.dead ? 0.2 : 1)\n \n circles\n .exit().remove()\n \n return svg.node()\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":162,"value":"part2 = {\n const max = d3.max(Object.values(track), d => d.p[1])\n let carts = [...initial.carts]\n let n = 0\n \n while (carts.filter(c => !c.dead).length > 1) {\n carts = _.sortBy(carts, c => c.p[1] * max + c.p[0])\n \n for (let cart of carts) {\n if (cart.dead)\n continue\n carts = carts.map(c => c === cart ? tick(cart) : c)\n const bam = crashes(carts.filter(c => !c.dead))\n if (!_.isEmpty(bam))\n carts = carts.map(c => (c.p in bam) ? {...c, dead: true} : c)\n }\n\n // if (n % 10000 === 0)\n yield { carts, n }\n\n n++\n }\n \n yield { carts, n }\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":165,"value":"function crashes(carts) {\n return _.pickBy(_.countBy(carts, 'p'), c => c > 1)\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":112,"value":"part1 = {\n let carts = initial.carts\n let bam = []\n let n = 0\n \n // while (!crashes.length && false) {\n while (_.isEmpty(bam)) {\n // if (n % 10 === 0)\n yield { carts, bam, n }\n carts = carts.map(tick)\n bam = crashes(carts)\n n++\n }\n \n yield { carts, bam, n }\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":64,"value":"function tick(cart) {\n const curve = {\n '\\\\': {\n '^': '<',\n '>': 'v',\n 'v': '>',\n '<': '^',\n },\n '/': {\n '^': '>',\n '>': '^',\n 'v': '<',\n '<': 'v', \n }\n }\n \n // move\n const nextCart = { ...cart, p: move(cart.p, cart.ch) }\n // change direction?\n switch (track[nextCart.p].ch) {\n case '\\\\':\n case '/':\n nextCart.ch = curve[track[nextCart.p].ch][nextCart.ch]\n break\n case '+':\n nextCart.ch = changeDirection(cart.ch, cart.changes)\n nextCart.changes++\n break\n }\n\n return nextCart\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":98,"value":"function move(p, ch) {\n switch (ch) {\n case '^':\n return [p[0], p[1]-1]\n case '>':\n return [p[0]+1, p[1]]\n case 'v':\n return [p[0], p[1]+1]\n case '<':\n return [p[0]-1, p[1]]\n }\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":89,"value":"function changeDirection(ch, i) {\n const directions = [\n { // 0: left\n '^': '<',\n '>': '^',\n 'v': '>',\n '<': 'v',\n },\n { // 1: straight\n '^': '^',\n '>': '>',\n 'v': 'v',\n '<': '<',\n },\n { // 2: right\n '^': '>',\n '>': 'v',\n 'v': '<',\n '<': '^',\n },\n ]\n \n return directions[i % directions.length][ch]\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":73,"value":"track = initial.track","pinned":false,"hidden":false,"mode":"ojs"},{"id":27,"value":"$30","pinned":true,"hidden":false,"mode":"ojs"},{"id":17,"value":"lines = (debug ? test2 : input).split('\\n').filter(_.identity)","pinned":true,"hidden":false,"mode":"ojs"},{"id":20,"value":"viewof debug = checkbox({\n options: [{ value: \"toggle\", label: \"Debug\" }],\n value: \"\"\n})","pinned":false,"hidden":false,"mode":"ojs"},{"id":201,"value":"test2 = (await fetch('https://gist.githubusercontent.com/visnup/e71441597c60026f95678a99818c2877/raw/23893b4361148e127b430294d69cbe378c0faef0/test')).text()","pinned":false,"hidden":false,"mode":"ojs"},{"id":10,"value":"test = (await fetch('https://gist.githubusercontent.com/visnup/fa0563b91a3f5a2ef2e1f8330559cfc6/raw/f605ab4ac5d637653046447a565118c245616132/test')).text()","pinned":false,"hidden":false,"mode":"ojs"},{"id":8,"value":"input = (await fetch('https://gist.githubusercontent.com/visnup/fab62b1e93ba5b1a8534da5f963fb871/raw/3f11bc928fbafc2046fec9bc0781b19dfd602556/input')).text()","pinned":false,"hidden":false,"mode":"ojs"},{"id":4,"value":"_ = require('lodash')","pinned":false,"hidden":false,"mode":"ojs"},{"id":275,"value":"d3 = require('d3')","pinned":false,"hidden":false,"mode":"ojs"},{"id":19,"value":"import { checkbox } from '@jashkenas/inputs'","pinned":false,"hidden":false,"mode":"ojs"}],"files":"$W31","stdlib":"1","titling":"auto"}